Corrosion of refractory metals in liquid metal and gaseous environments

Conference · Tue Jan 01 04:00:00 EST 1991

OSTI ID:5533083

DiStefano, J R

In general, refractory metals and alloys are very compatible with liquid or boiling alkali metals. However, corrosion resistance of niobium and tantalum requires maintaining low oxygen in the system. When the refractory metal contains a strong oxide former (Zr, Hf), additional oxygen in the solid metal can be tolerated if it is tied up as a stable oxide (ZrO{sub 2}, HfO{sub 2}). In sodium or potassium systems, oxygen in either the liquid metal or refractory metal can contribute to reduced corrosion resistance. The mechanical properties of refractory metals are very sensitive to interstitial elements such as oxygen, nitrogen, hydrogen, and carbon. Oxidation in air or other oxidizing environments is rapid above 300 to 400{degree}C, and some type of protection must be provided (vacuum, inert gas, coating) if refractory metals are to be used at high temperatures. Oxidation of niobium and tantalum alloys is more complex than for molybdenum and tungsten due to the formation of different oxide phases that exhibit differing degrees of protectiveness. At low to intermediate temperatures niobium and tantalum also react with hydrogen environments, and embrittlement has been reported both from hydride formation as well as from solid solution effects. At high temperatures niobium and tantalum react with nitrogen or carbon to form very stable compounds while the nitrides and carbides of molybdenum and tungsten are considerably less stable. 10 refs., 10 figs.

• Research Organization: Oak Ridge National Lab., TN (USA)
• Sponsoring Organization: DOE; USDOE, Washington, DC (USA)
• DOE Contract Number: AC05-84OR21400
• OSTI ID: 5533083
• Report Number(s): CONF-910909-1-Draft; ON: DE91009555
• Country of Publication: United States
• Language: English

Related Subjects

36 MATERIALS SCIENCE
360102 -- Metals & Alloys-- Structure & Phase Studies
360105* -- Metals & Alloys-- Corrosion & Erosion
ALKALI METALS
ALLOYS
CHEMICAL REACTIONS
CORROSION RESISTANCE
ELEMENTS
FLUIDS
LIQUID METALS
LIQUIDS
METALS
NIOBIUM
NONMETALS
OXIDATION
OXYGEN
REFRACTORY METALS
TRANSITION ELEMENTS
TUNGSTEN